The goal of this proposal is to continue the UC Berkeley Molecular and Cell Biology (MCB) program of predoctoral training at the level of 50 predoctoral trainees per year, predominantly funding students in their first 2 years of graduate school. The 72 faculty associated with this training grant are field- leading scientists with ample research support and a strong commitment to mentoring. The program has a long-standing and defining principle: early and persistent emphasis on student training for an individually directed path to innovative research. The breadth of interests and interactions among the trainees and training grant faculty, combined with unique program requirements such as peer-group research presentations starting in the first year, encourage trainees to seek cross-disciplinary training opportunities. Another key tenet of the program is that the students share their knowledge by classroom teaching and participation in advanced seminar classes. One mission that the program does not have is a specific post-Ph.D. career path for the trainees: instead, the program promotes forward- thinking preparation for a well-informed choice among diverse post-Ph.D. careers. The program is strongly committed to recruiting and training students from diverse personal backgrounds. The Molecular Basis of Cell Function is the only training grant specific to, and the only training grant largely comprehensive for, the MCB graduate program. Training grant faculty research spans the 5 administrative Divisions of the Department (Biochemistry and Molecular Biology/ Cell and Developmental Biology/ Genetics, Genomics, and Development/ Immunology and Pathogenesis/ Neurobiology). The MCB graduate program has consistently ranked in the top 5 nationwide, substantiating the success of the training. Training grant faculty work through rotating assignments to enrich all components of the program: the research infrastructure, the set of broadly collaborative faculty, the adaptive training plan, and the high-caliber trainee pool with high minority representation. The program is set in a rich training environment, with groups brought together by a large number of shared activities, training opportunities, and research resources. Health Sciences Initiative funding from state and private donors enabled our increased focus on quantitative biology and biomedicaly relevant research through the training and research missions of the campus California Institute for Quantitative Biosciences and Li Ka Shing Center for Biomedical and Health Sciences. Additional focus on disease-relevant research is fostered by the Center for Emerging and Neglected Diseases, Berkeley Stem Cell Center, Cancer Research Laboratory, and Center for Computational Biology. )